The molecular basis of cellular interactions is not well understood. There is a large amount of evidence, however, implicating cell surface glycoconjugates in the phenomena of cell adhesion and differentiation in some systems. This proposed study will examine in detail the structures of the cell surface glycoprotein oligosaccharides from chicken embryo day 6 to day 17 dorsal and ventral neural retina and optic tectum-a system in which glyconjugates may participte in specific cell adhesion. For comparison and to allow an estimate of the capacities of embryonic cells to synthesize glycoprotein oligosaccharides, structural analyses will also be performed on cultured chicken embryo fibroblasts and myoblasts. Preliminary data indicate that the Asn-linked oligosaccharides from embryonic day-8 chick neural retina are unusual and different from those in chicken embryo fibroblasts, possibly due to differences observed in the activity of GlcNAc:UDP-gal galactosyltransferase. This proposal will test the hypotheses that (i) between the dorsal and ventral neural retina and optic tectum there are major differences in the structures of surface glycoprotein oligosaccharides and in the activities of glycosyltransferases and glycosidases, and (ii) within the neural retina at different stages of development the structures of the glycoprotein oligosaccharides are altered. Cells and tissues will be incubated with radioactive sugar precursors both in vivo and in vitro. The radiolabeled surface glycopeptides will be prepared and separated by serial lectin affinity chromatography and HPLC and the structures will then be determined by specific exo- and endoglycosidase treatments and methylation analysis. This detailed knowledge of the structures of surface glycoprotein oligosaccharides will allow for future experiments aimed at testing the hypothesis that glycoprotein oligosaccharides influence specific cell adhesion and differentiation within the neural retina and optic tectum.